3D CMOS Image Sensor Stacked Photodiode Transistor Bonding
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Solution Overview
Problem
Conventional CMOS image sensors face reduced quantum conversion efficiency due to transistors hindering light absorption by photodiodes, leading to lower light receiving efficiency.
Innovation Solution
A semiconductor device comprising a first integrated circuit with a photodiode and a first metal interconnect structure, and a second integrated circuit with a transistor and a second metal interconnect structure, connected through the metal interconnect structures, where the photodiode is isolated from transistors, increasing the effective photosensitive area and fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If photodiode and transistor circuit are integrated on the same chip, then device complexity is reduced and manufacturing is simplified, but light receiving efficiency and quantum conversion efficiency are reduced due to transistor obstruction
Solution Approach 1:
The device is segmented into two separate integrated circuits: a first integrated circuit containing the photodiode and a second integrated circuit containing the transistor circuit. This segmentation allows the photodiode to be isolated from transistor obstruction, improving light receiving efficiency while maintaining the benefits of integration through the bonding connection between the two circuits.
Solution Approach 2:
The patent transitions from a planar integration approach to a three-dimensional stacked architecture. By bonding the first integrated circuit (photodiode) and second integrated circuit (transistor) vertically together, the design utilizes the vertical dimension to separate light-receiving and signal-processing functions, eliminating mutual interference while maintaining compact form factor.
2Productivity
If transistor circuit is placed around photodiode, then pixel functionality is achieved, but effective photosensitive area and fill factor are reduced
Solution Approach 1:
By separating the photodiode and transistor circuit into different integrated circuits, the photodiode area is no longer constrained by surrounding transistors. The first isolation trenches in the first substrate define the photodiode region without transistor encroachment, maximizing the effective photosensitive area and fill factor while maintaining complete pixel functionality through the bonded interconnect structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances quantum efficiency and reduces power consumption by eliminating transistor obstruction around the photodiode, thereby improving light absorption and conversion efficiency.
Implementation Method 1
An image sensor is able to receive information of an optical image and convert the information into an electric signal
Implementation Method 2
The first integrated circuit and the second integrated circuit are connected together through the first metal interconnect structure and the second metal interconnect structure
Data Source
AI summary
A device includes a first integrated circuit containing a photodiode and a first metal interconnect structure connected to the photodiode, and a second integrated circuit containing a transistor and a second metal interconnect structure connected to the transistor. The first integrated circuit and the second integrated circuit are connected together through the first metal interconnect structure and the second metal interconnect structure. Since no transistor is present around the photodiode, the photodiode has an increased photosensitive area and an improved fill factor, resulting in an increase of the quantum efficiency, higher integration and lower consumption of the image sensor.